another reverb

[Austin Otto]

Update, actually the reverb is working on my Hr-40! Didn't realize it has a locking mechanism that just needed unlocking! Not too bad sounding. I still need to ramp up the high end however.

[Austin Otto]

I just tried out my new HR-40 at home and agree with the general consensus about the dull tone. I noticed, however, that the spring connected to the crystal makes a sound when tapped that is affected by the reverb volume control. Since I have no reverb from the cabinet otherwise, does this mean the crystal is good, but rather, I have an issue with the driver? I couldn't discern any vibration from the driver. You mentioned the transformer for the driver being a common issue.
Speaking of options (maybe this should be a new posting...) I definitely want to pump up the high end in this cabinet. I have the rotosonic speakers in the drum I got from you and I also have (2) 16 ohm 6x9 speakers somebody gutted from a Leslie 700. I also have the reverb system in my Leslie 900 (reverb unit and 6x9 speakers) that I could repurpose in the HR-40 if that made any sense at all.
When you say "just add in a horn driver" that probably means more than just "wiring in" another speaker or two I suspect?

[Ted Kendrick]

Kzinkmusic : That definitely the unit. The coils in the tank are ok. I'll just reverse engineer the board to test it. Like to use the whole assembly as is if possible.

[Austin Otto]

The serial numbers don't match my R-124,.

[kzinkmusic]

Hammond R-series organ reverb unit | eBay Looks very similar to this one

[Ted Kendrick]

So, any answer to the original question, the spring reverb on the lawn chair with the circuit board on top and the lever on the side to damp the springs? Maybe a diagram for the board.

[David Anderson]

I like your idea about changing out the treble side of the HR-40. I heard a HR-40 with the 2 twelves unhooked and, in their stead,2 4inch high frequency drivers. The sound was better than any stock cab, very full on the high end.

I think you can keep the twelves and just add in a horn driver to extend the HF response. The "treble" channel in Hammond cabinets covers 200Hz - 6kHz. 12" speakers like the ones you'd find in an HR-40 are going to peak between 2kHz and 4kHz, but will often fall off sharply above that. Only a few twelves have good output up to 6kHz.

It's only a 20 Watt amp, so you have lots of options.

[tmccann]

You could always stick a horn driver in there with a minimal crossover.

I did this at David's suggestion in my son's custom M3. I added a PRV driver with an 800 Hz high-pass filter and and L-pad to set the level. My son keeps the L-pad at 10 pretty much at all times.

Really sounds great, especially with a Neo Vent plumbed in through the Trek ELB-1A.

[kzinkmusic]

I like your idea about changing out the treble side of the HR-40. I heard a HR-40 with the 2 twelves unhooked and, in their stead,2 4inch high frequency drivers. The sound was better than any stock cab, very full on the high end.

[David Anderson]

With regard to the oil oil-tube reverb units, I can't be sure I've ever heard one working exactly as it did when new, but Sal Azzarelli described them as sounding like "playing organ inside a concrete culvert." I've never heard anyone rave about how great they sound even when working properly.

Some people have managed to retrofit new piezoelectric pickups into things like the small spring reverbs found in Farfisa Compact organs. (Crystal pickups are piezoelectric. That's how they work.) I guess you could figure out a way to do it with the oil-tube reverb.

Around the time Hammond came up with the necklace and modern spring tank reverbs, crystal pickups were becoming largely obsolete, and it's obvious that Hammond didn't want to try to keep supporting the oil tube units, so they proposed using a modern spring tank with an extra gain stage. The one advantage of crystal pickups is that they have a high output voltage.

In HR-40s, there can be multiple problems with the reverb. For some reason, the reverb drive transformers have a tendency to have the windings open up from wire corrosion.

And then the HR-40s don't sound that great, especially in smaller spaces. They sound a lot better in a large church sanctuary, which I guess was part of the design, but even there, they are weak on the high end, apparently on purpose. You have 2 x 12" speakers handling the treble, and they are firing through thick grille cloth. You could always stick a horn driver in there with a minimal crossover.

[Ted Kendrick]

That reverb unit has a very large dynamic driver and a crystal pickup. Most crystal elements of this age would be no good. I don't know if I will try to make this one work, just for grins. Found it in an old radio station.

[Austin Otto]

Speaking of "original" Hammond spring reverb, I'm planning to pick up an RT-2 with an HR-40 cabinet in very nice condition except that the reverb doesn't seem to work. I have read that even Hammond suggested replacing the reverb unit and adding a new reverb amp on that model. Has anyone repaired one? Is it worth saving any of those parts?

[Ted Kendrick]

And for your entertainment-the original Hammond spring reverb.

[Ted Kendrick]

The attachment didn't make it. Don't know why. I'll try again.

[Ted Kendrick]

Here's another unit I need identified. Hammond B-300 maybe?